1. Field of the Invention
The present invention relates to a semiconductor laser apparatus comprising cavities in correspondent with a plurality of light emitting units fabricated on the same substrate, and a laser coupler, a data reproduction apparatus and a data recording apparatus having the semiconductor laser apparatus, and a production method of the semiconductor laser apparatus.
2. Description of the Related Art
In recent years, an apparatus capable of recording and reproducing of a plurality of media such as CD (compact disk) and DVD (digital versatile disk) has been developed. When single apparatus is used to record/reproduce a plural types of media, the apparatus is required to have a system construction satisfying all the standards of media types included in the system. For example, at least two laser light emitting devices with different wavelengths have to be equipped in the same apparatus so as to perform recording/reproducing of both the CD and the DVD, that use laser lights with different wavelengths.
The device emitting laser lights with two different wavelengths may be realized by combining separate semiconductor laser devices emitting the two wavelengths and respective optical systems for the separate semiconductor laser devices. However, the combination of the separate devices and the optical systems may causes increase of a number of parts and a total cost of the apparatus, and prevent reduction of the apparatus size.
To resolve such disadvantages, a monolithic type semiconductor laser device had been developed. The monolithic type semiconductor laser device (so called two wavelength laser) has two active layers grown on the same substrate separately for emitting different wavelength lasers. FIGS. 10A and 10B are explanatory schematics illustrating a monolithic type semiconductor laser device. FIG. 10A is a plan view of the monolithic type semiconductor laser device. FIG. 10B is a cross sectional view showing a cross section taken on line X-X′ in FIG. 10A.
The semiconductor laser device may be produced, for example, by fabricating a n-GaAs buffer layer 2a on a substrate 1 consisting of n-GaAs, and, a laser diode A emitting 780 nm band wavelength laser light and a laser diode B emitting 650 nm band wavelength laser light on the n-GaAs buffer layer 2a. A separation between light emitting parts of the laser diode A and the laser diode B is less than 200 μm. For example, the separation may be set to less than 100 μm in many cases.
In the monolithic type semiconductor laser with the configuration described above, it is possible to keep a separation between the two laser lights into a smaller value with high precession since the active layers and the clad layers capable of emitting different wavelength laser lights are fabricated separately on the same substrate. Accordingly, an optical system at a subsequent stage may be shared, and it becomes possible to reduce a number of parts, a total cost of the apparatus, and a size of the apparatus.